Indeed. The flight operates from the domestic area and therefore the bus takes passengers from the aircraft to the UK Border. Departing, well we don't care who leaves the UK do we? The more annoying aspect of this is that the Edinburgh to LCY service often lands on the next gate, if I'm connecting it's very tempting to pop into the lounge door, but the long walk we must make.

To answer the orginial question, 30 minutes before departure is ok, 45 minutes gets you a drink or two. 1 hour is getting excessive.